Minimum cost of transport in Asian elephants: do we really need a bigger

摘要

Body mass is the primary determinant of an animal's energy requirements. At their optimum walking speed, large animals have lower mass-specific energy requirements for locomotion than small ones. In animals ranging in size from 0.8 g (roach) to 260 kg (zebu steer), the minimum cost of transport (COTmin) decreases with increasing body size roughly as COTmin proportional to body mass (M-b)(-0.316+/-0.023) (95% CI). Typically, the variation of COTmin with body mass is weaker at the intraspecific level as a result of physiological and geometric similarity within closely related species. The interspecific relationship estimates that an adult elephant, with twice the body mass of a mid-sized elephant, should be able to move its body approximately 23% cheaper than the smaller elephant. We sought to determine whether adult Asian and sub-adult African elephants follow a single quasi-intraspecific relationship, and extend the interspecific relationship between COTmin and body mass to 12-fold larger animals. Physiological and possibly geometric similarity between adult Asian elephants and sub-adult African elephants caused body mass to have a no effect on COTmin (COTmin proportional to M-b(0.007+/-0.455)). The COTmin in elephants occurred at walking speeds between 1.3 and similar to 1.5 ms(-1), and at Froude numbers between 0.10 and 0.24. The addition of adult Asian elephants to the interspecific relationship resulted in COTmin proportional to M-b(-0.277+/-0.046). The quasi-intraspecific relationship between body mass and COTmin among elephants caused the interspecific relationship to underestimate COTmin in larger elephants.